Many people sitting by a computer for long working periods suffer from tension and pain in neck and shoulders resulting in chronic strain injuries. Today's word processors do not give the same opportunities of so-called microbreaks as did the typewriters, for instance in the form of shifting sheets of paper or manually correcting the text. Long working periods with precision work using a mouse have also been found to cause strain in neck and shoulders and pain in the arm by which the mouse is operated, a so-called mouse arm.
Various keyboard holders are known, which are arranged to permit adjustment of the keyboard at an angle relative to the horizontal plane. For instance, U.S. Pat No. 5,351,897 discloses a keyboard holder which is adapted to be fixed to a desk top in a recessed position relative thereto and which has a flat panel and a mounting with a movable and a fixed part. The movable part, on which the flat panel is mounted, is pivotable about a horizontal axis which permits adjustment of the panel at a negative angle such that the keyboard upper side with the keys is facing away from or inclined downwards away from the user. The idea is that the keyboard, thanks to the recessed positioning of the holder relative to the desk top, should be located as close to the user's legs or knees as possible, and a slight negative angling of the keyboard results in a neutral position of the hands without any angling of the wrist. A drawback of this keyboard holder is that the operator is obliged to work sitting in a relatively static working position with a great, essentially right angle between the upper parts of the arms and the forearms and with the forearms extended essentially horizontally without any real possibility of changing the position.
Other keyboard holders, such as those according to U.S. Pat. Nos. 5,242,139 and 5,040,757, have a support for wrist and palm and are arranged to provide a slight angling of the keyboard from the user, but also these keyboard holders do not offer any possibility of changing the working position and relieving arms, shoulders and back.
The company Jargus at Karlsborg, Sweden, has for some time been selling a holder for keyboards in the form of an attachment, the carrier for the keyboard being raisable to a position where an upper side of the keyboard is directed away from the user at an angle of at least 30.degree. relative to the horizontal plane. However, the keyboard carrier of the Jargus holder is hingedly connected to the supporting part via a hinge which is turnable about a horizontal axis located essentially in the centre of the keyboard carrier. This means that the keyboard carrier must be located at a relatively great distance from the base to be able to make such a great angle as 30.degree. or more in its raised state. This is disadvantageous since it means that the holder will have a great thickness or height also in its lowered, horizontal position, which renders a comfortable working position when sitting down difficult or even impossible. If the holder is in fact placed on a level allowing a comfortable working position for the user's forearms, this will imply that the supporting part of the holder is placed on such a low level that this, and especially the base on which it stands, is on a level with the user's knees and thighs, and consequently he cannot place himself sufficiently close to the holder and the keyboard. To be able to reach the keys furthest away on the keyboard, the user must thus stretch himself forwards or alternatively raise the base and the keyboard holder, which will result in a considerably deteriorated working position for arms and shoulders.